Inmet on Tuesday said it has entered into confidentiality and standstill agreements with a number of interested parties. The company did not name the third parties.

First Quantum is offering C$72 for each share of its smaller rival. The offer, announced in mid-December, tops its earlier bids of C$62.50 and C$70 per share.

If successful, the deal would give First Quantum control of the Cobre Panama project in Central America, which is one of the world's largest undeveloped copper deposits, easing its dependence on Africa and particularly Zambia.

Inmet said it expected the Cobre Panama project to drive a 176 percent increase in its copper output by 2018 and that the First Quantum offer does not take into account the increase in company's valuation once the project starts production.

Inmet's shares, which have gained 42 percent in the last three months, closed at C$70.94 on the Toronto Stock Exchange on Monday.